November 7, 2011

A Rant about 3d Printers

My 3D Printer — a RepRap — works really well, for an FDM printer. I’ve been printing lots of parts for my CNC design, and I have an Alpha prototype. I was assembling the prototype at a hacker space in Seattle called Metrix Create Space, when I decided to try an experiment — and since I didn’t have my printer with me, I used openScad’ project function to convert my design to something I could cut on their laser cutter.

Wow! What a difference in speed. This part would have taken me maybe 40 minutes to print, but was ready in literally a minute on the laser. Even though I have to pay for laser time, and pay for plywood, it was still worth it. I made three iterations and cuts in less time than a single print would have taken, even of a small part. Plus, their laser is far more accurate than my reprap — Variances in position between my model and actual part was around 0.02 mm. I don’t know of any RepRap owner who has variances that small. I was able to design without correcting for error! It was fantastic.

Which brings me to a thought. Additive manufacturing has been around for a long time now. The first FDM devices came to life in the 80s — so long ago, that the first patents on 3d printing have already expired. The RepRap exists because the MIT patent on additive manufacturing expired in 2007. Yet, most processes seem to be based on subtractive manufacturing, not additive. Why? I believe it’s because speed matters. Additive, especially when you start using processes like brass infusion — is very slow compared to subtractive. The costs of materials are about the same as well between methods — though the cost of tooling is a lot more with subtractive. I’m getting more and more convinced that a good CNC bot is the right choice for anyone making a RepRap. I view it this way — my laser cut part was essentially a plate with 6 holes in it. The holes were a standard size — a drill bit that size would easily be available. I had to remove, with high accuracy, 24mm square from the plate over those six holes. Whereas, if I had printed the part — I had to add 870 square mm of material. Subtractive was faster — because it did far less work to achieve the same result.